These studies were designed to determine whether M. pneumoniae, an established human pathogen, could induce pneumonia in chimpanzees. Six sero-negative, culture-negative young adult chimpanzees were inoculated intratracheally with a virulent strain shown to produce disease in human volunteers. All six animals became colonized with peak respiratory mycoplasma titers of 10 to the 6th power to 10 to the 8th power ccu/ml. The oropharyngeal and tracheal tissues remained colonized for up to 70 days and lungs for 26 days. Animals developed positive X-ray findings by day 12-16 which corresponded with peak lung colonization. Positive serum cold agglutinin titers were first observed at day 12 to 15, and persisted for as long as 48 days with peak titers ranging from 1:160 to 1:640. Serum antibody titers developed within two weeks and persisted throughout the three month study period. Animals became overtly ill within two weeks post-inoculation which corresponded with the onset of positive X-ray findings and peak colonization of lungs. All animals developed a persistent cough and some developed rhinitis, inflamed oropharyngeal tissues, diarrhea, and loss of appetite. Two control chimpanzees maintained in individual cages and in rooms separated and distant from the infected animals became infected on days 19 and 48, respectively and we were unable to detemine the means of transmission. Thus, the M. pneumoniae pneumonias induced in chimpanzees were remarkable similar to naturally occurring primary atypical pneumonia in patients and the infection in the chimpanzee animal model best reflects and parallels those in humans. Some of these data were reported earlier and a manuscript is in preparation.